Numerical Optimization of the Linear Dynamic Behaviour of Commercial Vehicles

The demands upon the dynamic behaviour of a vehicle can be stated as an optimization problem. The optimum solution is calculated using an iterative optimization algorithm. Scaling the problem by non-linear transformations reduces the number of iterations. Lagrange multipliers provide useful information about the sensitivity of the optimum with respect to changes of the constraints. The analysis of the dynamic behaviour is performed in the frequency domain. New structural variants are calculated using system synthesis. As an example, the engine, cab and wheel suspension systems of a tractor/semi-trailer have been optimized all together.     

Characteristics of truck traffic in Singapore

This paper presents the results of a project conducted to study the characteristics of truck traffic in Singapore. Detailed traffic surveys recording counts of vehicles by axle-configuration were performed at 219 sites over a period of nearly two years. The surveys covered 5 different road classes, namely expressways, arterials, collectors, industrial roads and local roads. It was found that the time distribution of truck travel were not the same among the five road classes. The peaking characteristics of truck traffic were less pronounced compared to passenger car traffic. The peak hour truck volume varied from 67.0% to 9.7% of the daily truck traffic as compared to 13.8% for passenger car traffic. The lane distribution pattern of truck traffic was studied in detail by road class, and was found to be a function of total directional traffic volume, total directional truck volume and the number of traffic lanes. Composition analysis was also carried out to study the lane use characteristics of single- and multiple-unit trucks.     

Choosing the wrong technology: Or how to spend billions and reduce transit use

In spite of a broad consensus among transportation analysts that bus rapid transit, whether operating on exclusive rights-of-way or on uncongested high occupancy vehicle lanes or general purpose limited access facilities, provides higher performance and has significantly lower costs per passenger trip than rail transit in medium and low density cities, nearly all Sunbelt cities are building or planning heavy or light rail systems. This paper reviews previous studies of the cost-effectiveness of heavy and light rail transit with bus-rapid transit and the growing experience with busways and transitways and concludes, once again, that some form of bus rapid transit would be a far more effective way of providing improved transit in these cities than heavy or light rail transit. Not only would bus rapid transit be substantially cheaper, but it would provide a higher quality of service than light or heavy rail transit for virtually all users. Finally, the paper speculates on the reasons for the continued, “blind” commitment to rail transit by policymakers in Sunbelt cities and on the refusal of policymakers in all but a few of these cities to even consider bus rapid transit.     

The effect of round-off error on computed solutions of trip distribution problems

Round-off error analyses of two versions of the Kruithof method are given. It is shown than an alternative implementation is numerically superior to the usual implementation. Since it also has the advantage of requiring less writing in secondary memory, and requires the same number of arithmetic operations, the case for always using the alternative implementation seems indisputable.     

The role of accessibility in basic transportation choice behavior

Accessibility measures reflect the level of service provided by transportation systems to various locations. Basic transportation choice behavior is defined to include those decisions of how many automobiles to own and how many trips to which destinations to make by automobile and by public transit. Here, these decisions are assumed to be made jointly by urban households and are conditional upon residential location decisions. It is the purpose of this paper to explore the role of accessibility as a causal factor in such basic transportation choice behavior.An economic utility theory model of choice behavior is postulated in which the benefits from making trips to specific destinations are reflected by measures of destination attraction. Through determination of utility-maximizing trip frequencies, indirect utility functions are developed which include accessibility concepts. Behavioral implications of these concepts are proposed and contrasts are drawn to accessibility measures used in conventional segregated models of trip distribution, modal choice, and automobile ownership.Sensitivity analyses of alternative empirical definitions of accessibility in the choice model are conducted using data from the Detroit Regional Transportation and Land Use Study — covering counties in southeastern Michigan. These analyses employ a multinomial logit estimation technique and focus on definitions of trip attraction. Results of these analyses indicate that more complicated attraction measures can be replaced by measures involving the proportion of either urban area population or urban area employment within a traffic analysis zone. Also, evidence is found that decision-makers in the case study area consider trips of up to 60 or even 90 minutes duration when evaluating accessibilities offered by alternative public and private transportation systems.     

Effects of subsidies on urban public transport

Because of a general trend of increasing costs of public transport operations and higher subsidies (in some cases accompanied by falling patronage) the European Conference of Ministers of Transport (ECMT) initiated a study of subsidisation and sought the help of the Transport and Road Research Laboratory. The study, in which eighteen countries took part, was concerned with the aims of subsidy, the sources and conditions attached to subsidy, trends in subsidies and the effect of subsidies on patronage, fares, service levels, costs and productivity.The qualitative information concerning the aims of subsidy was analysed in relation to the likelihood of achieving such aims, taking into account current experience of attempts to switch car drivers to public transport. The quantitative information on trends referred to public transport stage services covering where possible the entire country and relating to the period 1965–77; these data were supplemented by data from 59 cities in different parts of the world collected in the course of a TRRL-sponsored study of travel demand factors. The relationship between patronage and service levels, and between subsidies and various operating factors, including costs and productivity, were studied using regression analysis and the general conclusion reached was that although the major part of the subsidy paid was reflected by reduced fares and improved service levels there may well have been some leakage into higher unit costs and manning levels.     

Analysis of equilibrium automobile holdings in Israel with aggregate discrete choice models

Models of household vehicle ownership decisions do not suffice as a basis for forecasting the size and composition of aggregate vehicle holdings. Forecasting applications require that such models be imbedded in systems describing the operation of the automobile market. This paper presents a new model of short run equilibrium in the automobile market. The short run is a period within which new car designs and prices are fixed but used car prices adjust competitively to market forces. The magnitude and mix of new car sales, the extent of used car scrappage and the composition of used car holdings are determined in equilibrium with used car prices. An econometric version of the market model has been estimated on Israeli data and applied to analyze the impact of vehicle tax policy on automobile holdings in Israel. The paper describes this application.     

TDRM: A peer-to-peer-based taxonomy data ring model

Peer-to-peer (P2P) networks are widely used due to their good scalability and robustness. This paper considers the characteristics of data sources which use some taxonomy hierarchies to classify and organize their data objects, combines P2P techniques, and proposes a P2P based taxonomy data ring model (TDRM). The model makes full use of the semantic information contained in taxonomy hierarchies, places the data objects having similar semantics together, and organizes them into one dimensional ring structure. Super-peers dynamically join the ring according to the requirement. The routing connections among super-peers are created, which are similar to Chord ring, thus a semantics based structured super-peer network is formed. Experiments show that the model has good scalability and search efficiency.     

Pulsed eddy current signal denoising based on singular value decomposition

The noise as an undesired phenomenon often appears in the pulsed eddy current testing (PECT) signal, and it is difficult to recognize the character of the testing signal. One of the most common noises presented in the PECT signal is the Gaussian noise, since it is caused by the testing environment. A new denoising approach based on singular value decomposition (SVD) is proposed in this paper to reduce the Gaussian noise of PECT signal. The approach first discusses the relationship between signal to noise ratio (SNR) and negentropy of PECT signal. Then the Hankel matrix of PECT signal is constructed for noise reduction, and the matrix is divided into noise subspace and signal subspace by a singular valve threshold. Based on the theory of negentropy, the optimal matrix dimension and threshold are chosen to improve the performance of denoising. The denoised signal Hankel matrix is reconstructed by the singular values of signal subspace, and the denoised signal is finally extracted from this matrix. Experiment is performed to verify the feasibility of the proposed approach, and the results indicate that the proposed approach can reduce the Gaussian noise of PECT signal more effectively compared with other existing approaches.     

盾构施工参数对地表沉降的因素敏感性分析

依托北京地铁8号线某区间盾构隧道工程,首先从盾构施工参数的关联性进行分析,选取4个相对独立的施工参数。之后采用灰色关联分析方法,对盾构施工条件下引起的地表沉降进行因素敏感性分析。分析结果表明,各施工参数对地表沉降的敏感性从大到小依次为土仓压力、同步注浆量、刀盘扭矩、同步注浆压力,以期对未来类似工程盾构施工参数优化和沉降控制研究提供借鉴。